Telephone-transmitter.



Vif. L. SPENGE. TELEPHONE TRANSMTTER.

APPLICATION FILED JUNE 6,1913.

Illini narran sierras P iirnnr oFFioE.

JESSE L. SPENCE, 0F NEW YORK, N. Y., ASSIGNOR T0 ELECTICAL EXPERIMENTCOMPANY, INC., A CORPORATION OF NEW YORK.

imitare?.

Specification of Letters Patent.

Application filed .Tune 6, 1913. Serial No. 772,087.

To all'uwm t may concern.' y

Be it .known that I, JESSE L. SrnNoii, a citizen of the United States,residing at New York, in the county of New York and State of New York,have invented certain new and useful Improvements in TelephoneTransmitters, and I do hereby declare the following to be a full, clear,and exact description of the invention, such as will enable othersskilled in the art to which it appertains to make and use the same.

The principal object' ct' the present invention is the production of atelephone tra'nsmitter capable of delivering to the transmitting mediuma form of wave more strictly conforming to the acoustic wave to be reproduced than has been possible hitherto. The result is materiallyimproved enunciation at the receiving end of the system, which isparticularly noticeable in loud speaking telephones.

One of the principal causes of distortion of sounds as iinally receivedover a telephone is found in the fact that the transmitter diaphragmsagainst which the speakers voice is directed tend to impose anartificial vibratory -law upon the wavel to be transmitted, either.owing tothe-bending of the diaphragm itself or to its attachment to eX-ternal devices so constructed or mounted as to have their own period ofvibration. The present improvement avoids Kthese objections by luse of asubstantially rigid diaphragm and a mounting for the same of anaperiodic nature, whereby neither the diaphragm itself nor any externalpart connected therewith tends to impose an 'artiiicialperiodicity uponthe resultant wave transmitted.

My improved transmitter may be used upon ordinary telephones, 'or in.connection with wireless telephonie systems.

The accompanyingr drawing is a vertical section of a preferredembodiment of my invention.

`Within the usual casing 10 is placed a conducting cup 11, preferablyinsulated from the casing where this latter is made of metal, as in thepreferred form shown. This cup, is connected to one out-going wire 12,while the .other out-going wire 13 is connected to the, diaphragm, asfor instance through the l casing 10 itself, as shown. vWithin the cap11 is placed the carbon dust or powder, or other microphonic material 14against which, (in my preferred form) the diathe same when not, iiiuse.

that cushions so used serve as an aperiodic' voice. I

' phragm 15 is made to bear directly. Owing to the fact that-thediaphragm is relatively inflexible, I am able to use a thin plate ofcarbon in this connection, and thus get the advantage ot' carbon againstcarbon without resort to anv attachments on the diaphragm. I prefer tointer-pose a soft felt layer 16 between the sides of the microphonicmass or masses and the cup 1l. rlhe conducting diaphragm 15 rests withits edge in contact with the metallic container or casing 10. as lshownin the drawing, and is thereby broughtl into electrical connection withone of the vleading-in wires 13.

preserved by two delicate annular air cushions 17 and 18, preferably ofthin rubber,

which make light contact with thefedge of-i the diaphragm and act merelyto support I have found I have found that a transmitter.. con structedsubstantially as described causes a movement of pure translation to beimposed upon the diaphragm 15, thus bringing int-o uniform and eiiieientaction all the particles or microphonie masses 14 within the cup 11.

Patented sept. 29, i914.'

I do not con fine myself to this expedient for bringing the diaphragminto the circuit, however. The proper position of the 'diaphragm is Thisfollows from the movement ofthe in- 1flexible diaphragm always parallelto the position of silence.

In certain forms of apparatus hitherto used, air cushions have beenemployed to clamp al diaphragm irmly in place, for damping purposes.Such a structure has no relation to thepresent invention, wherein asubstantially rigid diaphragm isso mounted as to acquire a movement oftranslation as 'a whole. A movement of this character involvespreservation of thevplane form of the diaphragm at all times, and thereresults a more evenly distributed pressure upon the microphonic materialthan Where the diaphragm bends in a-curve. This gives better efficiencyin the microphone and prevents local packing of the particles near thecenter, -inaking the microphone more durable.

I do' not limit myself to the details of construction described, asvarious changes may be made Without departing from the invention. v

WhatI claim is- 1. In a telephonie transmitter, a microphone, adiaphragm sutiiciently stift' to be substantially inflexible under theconditions of-use and mounted in operative relation with saidmicrophone, and a resilient mounting for said diaphragm of an aperiodiccharacter, adapted to permit movements of the diaphragm responsive tothe form of acoustic Waves with a minimum of distortion, substantiallyas described.

2. In a telephone transmitter, a microphone and a diaphragm in contacttherewith suiiciently stiff to be substantially inexible underconditions of use; in combination with a resilient aperiodic mountingfor said dia hragm adapted to permit moverments o. translation of thesame responsive to the impressed acoustic Waves with a minimum ofdistortion.

3. In a telephonie transmitter, a conducting casing, a microphone Withinthe same insulated therefrom, a conducting diar.phragm resting on itsedge upon and Within said casing, said diaphragm being sufiicient-lystiff to be substantially inflexible under conditions of use, and ayielding aperiodic mounting for said diaphragm, substantially asdescribed.

4:. In a telephonie transmitter, a microphone, a diaphragm suilicientlystift1 to be inflexible under conditions of use and mounted in operativerelation with said microphone, and a pair of delicate air cushionsmaking light contact with the opposite sides of the edge of saiddiaphragm and adapted to yield readily to the movements of the diaphragmincident to operation, substantially as described.

5. In a telephonie transmitter, a microphonic mass of carbon, a thin4carbon diaphragm suiiciently stift' to be inflexible under conditions ofuse in contact with said mass, and a yieldin aperiodic mounting for saiddiaphragm, su stantially as described.

In testimony whereof', I aiiix my signature, in presence of twoWitnesses.

KATHARINE C. MEAD, I-I. S. MACKAYE.

